Nevertheless, the results do support the finding that dense retrieval using DPR is (generally) more effective than sparse retrieval.
We confirmed that the effectiveness differences between DPR and BM25 in our replication results are statistically significant.
In all datasets except for SQuAD, DPR outperforms BM25; this is consistent with the original paper.
We further confirmed that for SQuAD, DPR is significantly worse than BM25.
As [1]} noted, Retriever\(_{\textrm {Multi}}\)  was trained by combining training data from all datasets but excluding SQuAD; these poor results are expected, since SQuAD draws from a very small set of Wikipedia articles.
